// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_QUIC_CRYPTO_CRYPTO_SECRET_BOXER_H_
#define NET_QUIC_CRYPTO_CRYPTO_SECRET_BOXER_H_

#include <stddef.h>

#include <string>
#include <vector>

#include "base/macros.h"
#include "base/strings/string_piece.h"
#include "base/synchronization/lock.h"
#include "net/base/net_export.h"

namespace net {

class QuicRandom;

// CryptoSecretBoxer encrypts small chunks of plaintext (called 'boxing') and
// then, later, can authenticate+decrypt the resulting boxes. This object is
// thread-safe.
class NET_EXPORT_PRIVATE CryptoSecretBoxer {
public:
    CryptoSecretBoxer();
    ~CryptoSecretBoxer();

    // GetKeySize returns the number of bytes in a key.
    static size_t GetKeySize();

    // SetKeys sets a std::list of encryption keys. The first key in the std::list
    // will be used by |Box|, but all supplied keys will be tried by |Unbox|, to
    // handle key skew across the fleet. This must be called before |Box| or
    // |Unbox|. Keys must be |GetKeySize()| bytes long.
    void SetKeys(const std::vector<std::string>& keys);

    // Box encrypts |plaintext| using a random nonce generated from |rand| and
    // returns the resulting ciphertext. Since an authenticator and nonce are
    // included, the result will be slightly larger than |plaintext|. The first
    // key in the std::vector supplied to |SetKeys| will be used.
    std::string Box(QuicRandom* rand, base::StringPiece plaintext) const;

    // Unbox takes the result of a previous call to |Box| in |ciphertext| and
    // authenticates+decrypts it. If |ciphertext| cannot be decrypted with any of
    // the supplied keys, the function returns false. Otherwise, |out_storage| is
    // used to store the result and |out| is set to point into |out_storage| and
    // contains the original plaintext.
    bool Unbox(base::StringPiece ciphertext,
        std::string* out_storage,
        base::StringPiece* out) const;

private:
    mutable base::Lock lock_;
    //  GUARDED_BY(lock_).
    std::vector<std::string> keys_;

    DISALLOW_COPY_AND_ASSIGN(CryptoSecretBoxer);
};

} // namespace net

#endif // NET_QUIC_CRYPTO_CRYPTO_SECRET_BOXER_H_
